Profession-grinding has to me been a pain as a multiboxer ... today I have to following setup:

Main: Herbalism / Skinning
Alt 1: Letherworking / Tailoring
Alt 2: Mining
Alt 3: Jewelcrafting / Letherworking
Alt4: Alchemy / Encanting / First Aid

1) Herbalism + Skinning on the main is deadeasy ... I just skin what I kill, and I see all the herbs on the minimap.
2) Letherworking: I lack A LOT of medium Leather, so either I have to go back to a zoone where it drops or buy it from AH.
3) Tailoring: I could feed 3 tailors with the number of cloth I have!
4) Mining ... since I have this on an Alt I dont see the nodes from time to time, meaning a miss quit a few ... resulting in me having to do separate mining-runs to make sure my mining-skill equals the zoon Im currently in.
5) Jewelcrafting: Since Im always on the short side with mining my jewelcrafter dont get the mats she needs ... resulting in me not keeping up the jewelcraft-grind.
6) Alechmy: Supported by my main ... not a big issue.
7) Enchanting: Supported by all drops + letherworking + tailoring ... dead easy.

But (now for the big BUT): Once I have leveld ~5 levels I need to grind up all none-gathering-proffession, which means I have to run around in IF / Exodar / Stormwind for a good 2 hours just to visit all proffesion-trainers ...... and I MUCH rather kill stuff that run around IF for 2 hours.